Joint surface pressure distribution prediction method for dynamic analysis of aluminum-steel bolt connecting piece

Abstract

The invention discloses a joint surface pressure distribution prediction method for kinetic analysis of an aluminum-steel bolt connecting piece, which comprises the following steps: determining geometric parameters influencing the pressure distribution of the joint surface, carrying out mathematical representation on the pressure distribution of the joint surface by adopting a polygonal function, and changing the geometric parameters to carry out statics analysis of multiple groups of finite elements, so as to predict the pressure distribution of the joint surface. Obtaining a mathematical representation parameter set of the pressure distribution of the joint surface; performing quartic polynomial fitting on the mathematical characterization parameters of the pressure distribution of the joint surface and the geometric parameter set to obtain a mathematical relationship between the mathematical characterization parameters of the pressure distribution of the joint surface and the geometric parameters; and correcting the joint surface pressure distribution prediction model by considering the changed bolt pre-tightening force. The invention provides the joint surface pressure distribution prediction method for dynamic analysis of the aluminum-steel bolt connecting piece, and important practical values are provided for calculation of the joint surface connection rigidity, prediction of the dynamic performance of the bolt connecting piece and evaluation of the cyclic fatigue life.

Description

Technical Field

[0001] The invention relates to a method for predicting pressure distribution on a joint surface of a dissimilar material mechanical connector, and in particular to a method for predicting pressure distribution on a joint surface used for dynamic analysis of an aluminum-steel bolt connector. Background Art

[0002] Bolted connection is a reliable connection method and is widely used in mechanical structure connection. Bolted joints transmit loads and motions through the contact interface, and the mechanical properties of the joint surface restrict the overall performance of the structure. In the dynamic working condition of bolted joints, the bolt preload often changes, which makes it difficult to characterize and quantify the pressure distribution of the joint surface. The pressure distribution of the joint surface has an important influence on the connection stiffness and dynamic performance of the bolted joint surface. Therefore, a pressure distribution model that is easy to mathematically characterize and calculate is proposed, which is used to update the dynamic parameters such as the joint surface pressure distribution in real time during the overall dynamic analysis of the bolted joint. It is of great significance to the prediction of the connection stiffness of the bolted joint and the analysis of the dynamic performance.

[0003] At present, the pressure distribution of the joint surface of bolted connection is mainly obtained by experimental method. However, when carrying out work scenarios such as forward design of bolted connection, it is costly to obtain a large number of bolted connection test pieces. It is difficult to statistically analyze its changing rules through simulation method and polynomial mathematical characterization, and the characterization parameters lack physical meaning. Therefore, the present invention establishes a prediction model for the pressure distribution of the joint surface of aluminum-steel bolted connection with the nominal diameter of the bolt, the thickness of the steel connecting plate, the thickness of the aluminum connecting plate and the bolt preload as influencing factors. The pressure distribution of the joint surface can be predicted in real time and dynamically according to the geometric parameters of the aluminum-steel bolted connection and the bolt preload, which can effectively solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting the pressure distribution of a joint surface for dynamic analysis of an aluminum-steel bolt connection. The present invention determines a geometric parameter that affects the pressure distribution of the joint surface, determines a preload of an anchor bolt, mathematically characterizes the pressure distribution of the joint surface using a broken line function, performs finite element statics analysis under N groups of different geometric parameters and obtains a set of mathematical characterization parameters for the pressure distribution of the joint surface, performs a fourth-order polynomial fitting on the geometric parameter set and the set of mathematical characterization parameters for the pressure distribution of the joint surface, obtains a mathematical relationship between each mathematical characterization parameter of the pressure distribution of the joint surface and the geometric parameter, and finally multiplies the numerical value of the pressure distribution of the joint surface that can be determined by the geometric parameter by the ratio of the preload of the bolt to be predicted to the preload of the anchor bolt, thereby establishing a prediction model for the pressure distribution of the joint surface of an aluminum-steel bolt connection based on the geometric parameter and the bolt preload as parameter input, laying a foundation for the calculation of the connection stiffness of the joint surface, the prediction of the dynamic performance of the overall bolt connection, and the evaluation of the cyclic fatigue life.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A method for predicting pressure distribution on a joint surface for dynamic analysis of an aluminum-steel bolt connection comprises the following steps:

[0007] (1) A three-dimensional geometric model of the bolt connector is established according to its geometric features. The bolt connector is a single-bolt connection structure, including a bolt, a nut, a steel connecting plate and an aluminum connecting plate. The steel connecting plate, the aluminum connecting plate and the nut are simplified into annular cylindrical structures, and the bolt head is simplified into a cylindrical structure. The threaded connection part is ignored, and the bolt gap remains unchanged in multiple sets of finite element statics analysis.

[0008] (2) Import the three-dimensional geometric model of the bolted connection into the finite element analysis software, set the material properties of the three-dimensional geometric model of the bolted connection, perform finite element meshing on the three-dimensional geometric model, and use sweeping meshing for steel and aluminum connection plates. The steel and aluminum connection plates should have at least four layers of mesh in the thickness direction to ensure analysis accuracy, and obtain the finite element model of the aluminum-steel bolted connection;

[0009] (3) creating a path on the steel connecting plate or aluminum connecting plate side of the joint surface of the finite element model of the aluminum-steel bolt connection to output the joint surface pressure distribution data, where the starting point and end point of the path are the bolt edge and the outer edge of the connecting plate respectively;

[0010] (4) The bolt preload is applied to the surface of the bolt hollow rod in the finite element model of the bolted joint. The bolt preload can be set to any value but must remain unchanged in subsequent multiple finite element statics analyses as the anchor bolt preload;

[0011] (5) Define each contact pair of the bolted joint: the contact mode of the bolt-nut contact surface is "binding", the contact mode of the bolt-connecting plate contact surface, the nut-connecting plate contact surface, and the steel connecting plate-aluminum connecting plate contact surface is "friction", and the friction coefficient is 0.15;

[0012] (6) Perform static analysis on the finite element model of the bolted joint in the pre-tightened state to obtain the pressure distribution data of the joint surface on the path;

[0013] (7) mathematically characterizing the pressure distribution of the bonding surface based on the broken line function, and fitting the mathematical characterization parameters of the broken line function by the least squares method;

[0014] (8) Changing the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate to obtain N groups of different combinations of the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate, and using them as the input of the prediction model fitting; modifying the geometric dimensions of the bolted connection according to the N groups of different geometric parameter combinations and performing static analysis to obtain N groups of different broken line function mathematical representation parameter data sets, and using them as the prediction model fitting output;

[0015] (9) Performing a fourth-order polynomial fitting on the geometric parameter set of the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate and the broken line mathematical representation parameter set to obtain a mathematical relationship between the broken line function mathematical representation parameters and the geometric parameters;

[0016] (10) By multiplying the numerical value of the joint surface pressure distribution that can be predicted by the geometric parameters by the ratio of the bolt preload to be predicted to the anchor bolt preload, the joint surface pressure distribution of the aluminum-steel bolt connection with different bolt nominal diameters, steel connecting plate thicknesses, aluminum connecting plate thicknesses, and bolt preloads can be predicted.

[0017] The pressure distribution of the aluminum-steel bolt connection in step (7) is mathematically characterized as a broken line function. The pressure generally increases with the radial distance and is expressed as two broken lines with different decay rates. The segmentation points of the two broken lines are fixed points, as shown in formula (1):

[0018]

[0019] In formula (1), k1 is the slope of the first line segment, k2 is the slope of the second line segment, r is the radial distance from the edge of the screw hole, and r max The maximum radius of the pressure distribution on the joint surface, r0 is the segmentation point of the broken line function.

[0020] The step (7) is based on the least squares method to fit the broken line function characterization parameters of the pressure distribution of the bonding surface, which is specifically as follows:

[0021] Extract the finite element static analysis results and determine r0 and r according to the pressure distribution characteristics in the finite element static analysis results. max ; The finite element static analysis results include the data points located on the inner broken line (radial distance 0 ~ r0): (r1, p1), (r2, p2)... (r m ,p m ) and the outer broken line (radial distance r0~r max ) data points: (r m+1 ,p m+1 ), (r m+2 ,p m+2 )…(r n ,p n );

[0022] Calculate the average radial distance between two polyline segments:

[0023]

[0024] In formula (2), is the average radial distance of the data points on the inner polyline, is the average radial distance of the data points on the outer polyline;

[0025] Calculate the average pressure of each of the two broken lines:

[0026]

[0027] In formula (3), is the average pressure of the data points on the inner broken line, is the average pressure of the data points on the outer broken line;

[0028] The fitting target of the inner broken line is: p a =k1x+b1, then the fitting target of the broken line is: p b =k2x+b2;

[0029] Calculate the residual sum of squares of the data points of the two segments of the polyline:

[0030]

[0031] In formula (4), V a is the residual sum of squares of the data points on the inner polyline, V b is the residual sum of squares of the data points on the outer polyline;

[0032] The fitting calculation results of k1 and k2 can be obtained by taking partial derivatives of the above residual sum of squares with respect to k1 and k2 respectively:

[0033]

[0034] In the step (8), stretching or compression is performed in the ANSYS Workbench SpaceClaim module to quickly modify the geometric parameters of the three-dimensional geometric model of the bolt connector and import it into the ANSYS Workbench finite element analysis module.

[0035] In step (9), k1, k2 and r max The quartic polynomial fitting objective function is:

[0036]

[0037] In formula (6), f1(m,x,y), f2(m,x,y), and f3(m,x,y) are k1, k2, and r respectively. maxThe fitting objective function is: m, x, and y are the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate, respectively. k1, k2, r respectively max Coefficients in the fitting objective function, m i 、x j ,y k are the nominal diameter of the bolts, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate in each set of finite element simulations.

[0038] In step (10), the pressure distribution of the joint surface of the bolt preload to be predicted is equal to the pressure distribution of the joint surface under the anchor preload multiplied by the ratio of the preload to be predicted to the anchor preload. As shown in formula (7):

[0039]

[0040] In formula (7), N0 is the anchor bolt preload, N is the bolt preload to be predicted, P(r) is the pressure distribution of the joint surface under the preload to be predicted, and N / N0 is the ratio of the target bolt preload to the anchor bolt preload.

[0041] Compared with the prior art, the present invention has the following beneficial technical effects:

[0042] The method for predicting the pressure distribution of the bonding surface for dynamic analysis of aluminum-steel bolt connectors proposed in the present invention is suitable for aluminum-steel bolt connectors with various standard bolt models, geometric dimensions and bolt preloads. In the ANSYS Workbench Space Claim module, the bolt nominal diameter, the steel connecting plate and the aluminum connecting plate thickness are changed to obtain N groups of different geometric parameter combinations. After finite element static analysis, the pressure distribution data of the bonding surface of the aluminum-steel bolt connector is obtained, and the pressure distribution of the bonding surface is mathematically characterized by a broken line function to obtain N groups of broken line function mathematical characterization parameter sets. The bolt nominal diameter, aluminum connecting plate thickness, steel connecting plate thickness parameter set and the broken line function mathematical characterization parameter set are fitted with a fourth-order polynomial to obtain the mathematical relationship between the mathematical characterization parameters of the bonding surface pressure distribution and each geometric parameter. Finally, the bonding surface pressure value under the anchor bolt preload that can be predicted by the geometric parameters is multiplied by the ratio of the bolt preload to be predicted and the anchor bolt preload, so that the bonding surface pressure distribution under different bolt nominal diameters, steel connecting plate thicknesses, aluminum connecting plate thicknesses and bolt preloads can be predicted. Compared with the conventional experimental method, the aluminum-steel bolt connection interface pressure distribution prediction method of the present invention has the advantages of significant cost reduction and dynamic real-time prediction, which provides important practical value for the dynamic prediction and dynamic analysis of the connection stiffness of the bolt connection interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1The present invention is a flow chart of a method for predicting pressure distribution on a joint surface for dynamic analysis of an aluminum-steel bolt connection.

[0044] Figure 2 It is the three-dimensional geometric model of the bolt connection.

[0045] Figure 3 Finite element model mesh of bolted connection.

[0046] Figure 4 is the joint surface path of the bolted connection.

[0047] Figure 5 It is the pressure distribution cloud diagram of the joint surface.

[0048] Figure 6 is the radial pressure distribution of the joint surface.

[0049] Figure 7 Comparison between the pressure distribution on the joint surface based on the prediction model and the simulation, where (a) is the anchor preload of 35000N and (b) is the target preload of 60000N. DETAILED DESCRIPTION

[0050] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0051] The present invention proposes a prediction method for the pressure distribution of the bonding surface of an aluminum-steel bolt connection. A three-dimensional geometric model is established according to the geometric characteristics of the bolt connection. The radial distribution of the pressure on the bonding surface of the aluminum-steel bolt connection is obtained based on the finite element statics analysis. A broken line function is used to mathematically characterize the pressure distribution on the bonding surface. The geometric parameters are changed and multiple groups of finite element statics analysis are performed to obtain a set of mathematical characterization parameters of the broken line function. The mathematical characterization parameters of the broken line function and the geometric parameters are fitted with a fourth-order polynomial. The bonding surface pressure value under the anchor bolt preload that can be predicted by the geometric parameters is multiplied by the ratio of the bolt preload to be predicted and the anchor bolt preload. Figure 1 , the method comprises the following steps:

[0052] (1) According to the geometric characteristics of the bolt connector, a geometric model of the bolt connector is established based on the ANSYS Workbench SpaceClaim module. The bolt connector is a single bolt connection structure, including a bolt, a nut, a steel connecting plate and an aluminum connecting plate. The steel connecting plate, the aluminum connecting plate and the nut are simplified to an annular cylindrical structure, the bolt head is simplified to a cylindrical structure, the threaded connection part is ignored, and the bolt gap is kept at 0.5 mm.

[0053] like Figure 2The figure shows the geometric model of the bolted connection, 1 is the bolt, 2 is the steel connection plate, 3 is the aluminum connection plate, and 4 is the nut. The specific geometric parameters are: the bolt nominal diameter is 12mm, the upper and lower plates are cylindrical plates with an inner diameter of 6.5mm and an outer diameter of 22.5mm, and the thickness of the upper and lower plates are 14mm and 4mm respectively.

[0054] (2) Import the above three-dimensional geometric model into the finite element static analysis module of ANSYS Workbench, and set the material properties of the bolts, nuts, steel connecting plates, and aluminum connecting plates in the three-dimensional geometric model respectively. The upper plate is a steel connecting plate, and the lower plate is an aluminum connecting plate. The material properties include elastic modulus, Poisson's ratio, and density. The three-dimensional geometric model is meshed, and the meshing method of the upper and lower plates is sweeping, and a finite element model of the aluminum-steel bolt connection is created.

[0055] like Figure 3 It is a 1mm finite element mesh with 215105 nodes and 47220 elements.

[0056] (3) Create four contact pairs based on the generated solid mesh, namely the contact surface between the bolt and the upper plate, the contact surface between the upper plate and the lower plate, the contact surface between the lower plate and the nut, and the contact surface between the bolt and the nut. The contact mode of the bolt and nut contact surface is "binding", and the contact mode of the bolt-connecting plate contact surface, the nut-connecting plate contact surface, and the steel connecting plate-aluminum connecting plate contact surface is "friction", and the friction coefficient is set to 0.15. Add bolt preload to the annular surface of the bolt hollow rod. Create a local coordinate system at the center of the screw hole on the joint surface, add a path to the local coordinate system, the starting point of the path is the edge of the screw hole, and the end point of the path is the edge of the upper plate.

[0057] like Figure 4 It is a path created on one side of the upper plate of the joint surface. The starting point of the path is located on the inner diameter of the steel connecting plate, and the end point is located on the outer edge of the steel connecting plate.

[0058] (4) After applying a preload of 35000N on the surface of the bolt hollow rod, a static analysis of the aluminum-steel bolt connection is performed. Figure 5 The pressure distribution cloud diagram of the joint surface is shown. Figure 5 It can be seen that the pressure distribution characteristics of the joint surface are that the contact pressure is evenly distributed along the circumference of the screw hole, decreases radially along the joint surface, has a smaller negative slope before the segmentation point, and a larger negative slope after the segmentation point. After reaching the maximum action radius, the contact pressure becomes 0. The pressure distribution in the radial direction of the joint surface is as follows: Figure 6 shown.

[0059] (5) According to the pressure distribution characteristics of the joint surface, the pressure distribution of the bolted joint surface is mathematically characterized by a broken line function, as shown in formula (1):

[0060]

[0061] In formula (1), k1 is the slope of the first line segment, k2 is the slope of the second line segment, r is the radial distance from the edge of the screw hole, and r max The maximum radius of the pressure distribution on the joint surface, r0 is the segmentation point of the broken line function. Since the pressure on the joint surface is evenly distributed around the screw hole, the mathematical expression of formula (1) specifically refers to the mathematical representation of the pressure distribution on the joint surface of the aluminum-steel bolt connection along the radial direction of the screw hole.

[0062] The parameters of the broken line function characterization based on the least squares method fitting the pressure distribution of the bonding surface are:

[0063] Extract the finite element static analysis results and determine r0 and r according to the pressure distribution characteristics in the finite element static analysis results. max ; The finite element static analysis results include the data points located on the inner broken line (radial distance 0 ~ r0): (r1, p1), (r2, p2)... (r m ,p m ) and the outer broken line (radial distance r0~r max ) data points: (r m+1 ,p m+1 ), (r m+2 ,p m+2 )…(r n ,p n );

[0064] Calculate the average radial distance between two polyline segments:

[0065]

[0066] In formula (2), is the average radial distance of the data points on the inner polyline, is the average radial distance of the data points on the outer polyline;

[0067] Calculate the average pressure of each of the two broken lines:

[0068]

[0069] In formula (3), is the average pressure of the data points on the inner broken line, is the average pressure of the data points on the outer broken line;

[0070] The fitting target of the inner broken line is: p a =k1x+b1, then the fitting target of the broken line is: p b =k2x+b2;

[0071] Calculate the residual sum of squares of the data points of the two segments of the polyline:

[0072]

[0073] In formula (4), V a is the residual sum of squares of the data points on the inner polyline, V b is the residual sum of squares of the data points on the outer polyline;

[0074] The calculation results of k1 and k2 can be obtained by taking partial derivatives of the above residual sum of squares with respect to k1 and k2 respectively:

[0075]

[0076] (6) Change the geometric parameters of the simulation sample: nominal diameter of bolts, thickness of steel connecting plates, and thickness of aluminum connecting plates. The nominal diameters of bolts are 10mm, 12mm, 14mm, 16mm, 18mm, and 20mm, respectively. The thicknesses of steel connecting plates and aluminum connecting plates are 2mm, 4mm, 6mm, 8mm, 10mm, 12mm, and 14mm, respectively. 294 sets of geometric parameter sets are obtained by combining them. The geometric model of bolted joints can be quickly modified by stretching or scaling the three-dimensional geometric model in the ANSYS Workbench Space Claim module. After performing the corresponding finite element static analysis and broken line function mathematical representation, 294 sets of broken line function mathematical representation parameter sets of the joint surface pressure distribution under different geometric parameter combinations are obtained.

[0077] (7) Performing a fourth-order polynomial fitting on the parameter set of the bolt nominal diameter, the steel connecting plate thickness, and the aluminum connecting plate thickness and the parameter set of the broken line function mathematical representation to obtain a mathematical relationship between the broken line function mathematical representation parameters and the geometric parameters;

[0078] In the above quartic polynomial fitting, k1, k2 and r max The quartic polynomial fitting objective function is:

[0079]

[0080] In formula (6), f1(m,x,y), f2(m,x,y), and f3(m,x,y) are k1, k2, and r respectively. max The fitting objective function is: m, x, and y are the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate, respectively. k1, k2, r respectively max Coefficients in the fitting objective function, m i 、x j ,y k are the nominal diameter of the bolts, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate in each set of finite element simulations.

[0081] Within the range of geometric parameter changes, the pressure distribution of the aluminum-steel bolt connection interface under the bolt preload of 60000 N is predicted for a bolt nominal diameter of 14 mm, a steel connection plate of 9 mm, an aluminum connection plate of 5 mm, and a bolt preload of 60000 N. According to the mathematical relationship between the mathematical characterization parameters of the broken line function and the geometric parameters in (6), the mathematical characterization coefficients of the pressure distribution of the connection interface under the anchor preload of 35000 N are calculated: k1 = -27.2276; k2 = -38.6238; r max =5.4467mm. The maximum contact radius of the above pressure distribution value remains unchanged, and the value is multiplied by (60000 / 35000) to obtain the distribution prediction of the pressure on the joint surface of the aluminum-steel bolt connection under the bolt preload of 60000N, and a simulation comparison is performed for verification.

[0082] Comparison between the model prediction results and the finite element simulation results of the joint surface pressure distribution Figure 7 As shown in the figure, it can be seen that the two curves have a high degree of overlap and a small error. Therefore, the method for predicting the pressure distribution on the bonding surface for dynamic analysis of aluminum-steel bolt connections proposed in this patent can effectively predict the pressure distribution on the bonding surface of aluminum-steel bolt connections, laying the foundation for the calculation of the connection stiffness of the bonding surface. It has important practical value for predicting the dynamic performance of bolt connections under external loads and evaluating the cyclic fatigue life.

Claims

1. A method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints, wherein: The specific steps include: Step 1: creating a three-dimensional geometric model of an aluminum-steel bolt connector according to the geometric features of the aluminum-steel bolt connector, wherein the three-dimensional geometric model of the aluminum-steel bolt connector is composed of bolts, nuts, steel connecting plates, and aluminum connecting plates; Step 2: Import the 3D geometric model of the aluminum-steel bolt connector into the finite element analysis software, construct a finite element model of the aluminum-steel bolt connector and perform static analysis to obtain the pressure distribution results of the joint surface; Step 3: Use a broken line function to mathematically characterize the pressure distribution of the bonding surface. Fit and extract the broken line function characterization parameters for mathematical characterization of the pressure distribution of the bonding surface based on the least squares method. The broken line function characterization parameters are composed of slope k1, slope k2, maximum contact radius r max And the broken line function segmentation point r0; Step 4: Change the combination of the three geometric parameters of bolt nominal diameter, steel connecting plate thickness and aluminum connecting plate thickness, repeat steps (1) to (3) N times, and obtain N sets of different geometric parameter sets of bolt nominal diameter, steel connecting plate thickness and aluminum connecting plate thickness, as well as k1, k2, r max The mathematical representation parameter set of the broken line function is used as the fitting input of the prediction model, and the mathematical representation parameter set of the broken line function is used as the fitting output of the prediction model; Step 5: Set k1, k2 and r max The mathematical characterization parameter set of is fitted with the geometric parameter set of bolt nominal diameter, steel connecting plate thickness and aluminum connecting plate thickness by a quartic polynomial to obtain k1, k2 and r max The mathematical relationship between the nominal diameter of the bolt, the thickness of the steel connecting plate and the thickness of the aluminum connecting plate is used to construct a prediction model for the pressure distribution on the aluminum-steel bolt connection interface based on the nominal diameter of the bolt, the thickness of the steel connecting plate and the thickness of the aluminum connecting plate as input parameters; Step 6: The maximum contact radius r of the pressure distribution of the joint surface of the prediction model max The pressure distribution value of the joint surface is multiplied by the ratio of the bolt preload to be predicted and the anchor bolt preload to obtain a four-parameter prediction model for the pressure distribution of the aluminum-steel bolt connection joint surface, which includes the bolt nominal diameter, steel connecting plate thickness, aluminum connecting plate thickness and bolt preload.

2. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: In step 1, the steel connecting plate, aluminum connecting plate and nut of the aluminum-steel bolt connector are simplified to an annular cylindrical structure, the bolt head is simplified to a cylindrical structure, the threaded connection part is ignored, and the bolt gap remains unchanged in multiple sets of finite element static analysis.

3. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: In the step 2, the mesh of the finite element model of the aluminum-steel bolt connection should ensure at least 4 layers of mesh in the thickness direction of the steel connection plate and the aluminum connection plate; the path is added to one side of the steel connection plate or the aluminum connection plate on the bonding surface to view the static analysis results of the radial distribution of the contact pressure of the bonding surface, the starting point of the path is the edge of the screw hole, and the end point of the path is the outer edge of the bonding surface; the bolt preload can be set arbitrarily but needs to remain unchanged as the anchor preload and be applied to the surface of the bolt hollow rod.

4. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: In step 3, the pressure distribution of the aluminum-steel bolt connection increases with the radial distance and is expressed as two broken lines with different decay rates, which are mathematically represented as broken line functions. The segmentation points of the two broken lines are fixed points, as shown in formula (1): In formula (1), k1 is the slope of the first line segment, k2 is the slope of the second line segment, r is the radial distance from the edge of the screw hole, and r max The maximum radius of the pressure distribution on the joint surface, r0 is the segmentation point of the broken line function.

5. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: The parameters of the broken line function characterization of the pressure distribution of the bonding surface in step 3 are fitted based on the least squares method, and are specifically as follows: Extract the finite element static analysis results and determine r0 and r according to the pressure distribution characteristics in the finite element static analysis results. max ; The finite element static analysis results include the data points located on the inner broken line (radial distance 0 ~ r0): (r1, p1), (r2, p2)... (r m ,p m ) and the outer broken line (radial distance r0~r max ) data points: (r m+1 ,p m+1 ), (r m+2 ,p m+2 )…(r n ,p n ); Calculate the average radial distance between two polyline segments: In formula (2), is the average radial distance of the data points on the inner polyline, is the average radial distance of the data points on the outer polyline; Calculate the average pressure of each of the two broken lines: In formula (3), is the average pressure of the data points on the inner broken line, is the average pressure of the data points on the outer broken line; The fitting target of the inner broken line is: p a =k1x+b1, then the fitting target of the broken line is: p b =k2x+b2; Calculate the residual sum of squares of the data points of the two segments of the polyline: In formula (4), V a is the residual sum of squares of the data points on the inner polyline, V b is the residual sum of squares of the data points on the outer polyline; The fitting results of k1 and k2 can be obtained by taking partial derivatives of the above residual sum of squares with respect to k1 and k2 respectively:

6. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: In step 5, k1, k2 and r max The quartic polynomial fitting objective function is: In formula (6), f1(m,x,y), f2(m,x,y), and f3(m,x,y) are k1, k2, and r respectively. max The fitting objective function is: m, x, and y are the nominal diameter of the bolt, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate, respectively. k1, k2, r respectively max Coefficients in the fitting objective function, m i 、x j ,y k are the nominal diameter of the bolts, the thickness of the steel connecting plate, and the thickness of the aluminum connecting plate in each set of finite element simulations.

7. The method for predicting the pressure distribution on the joint surface for dynamic analysis of aluminum-steel bolted joints according to claim 1, characterized in that: The pressure distribution of the joint surface of the bolt preload to be predicted in step 6 is equal to the pressure distribution of the joint surface under the anchor preload multiplied by the ratio of the preload to be predicted to the anchor preload, as shown in formula (7): In formula (7), N0 is the anchor bolt preload, N is the bolt preload to be predicted, P(r) is the pressure distribution of the joint surface under the preload to be predicted, and N / N0 is the ratio of the bolt preload to be predicted to the anchor bolt preload.

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